2.3. Measurement of water uptake by clay and sandy loam soils in
presence of swollen interpenetrating polymer network
Clay and sandy loam soil samples were used for laboratory
experiment. These samples were collected from the upper layer of
respective soil. The soil samples were air dried, mixed and crushed
to 2 mm particle size.
Accurately weighed dried interpenetrating network hydrogel
samples were taken in tea bags (100 mesh nylon screen) and were
immersed in 100 ml of distilled water. The samples were allowed
to soak water for 24 h. Tea bags were taken out from the distilled
water and were kept in air for two minutes to remove excess
water. Tea bags with swollen samples were added to known
weight of dry clay and sandy loam soils. After every 4 h time
intervals the tea bags with swollen samples were taken-out,
wiped with tissue paper and were weighed until equilibrium was
attained [24].
2.4. Loading of urea in interpenetrating polymer network
Urea solution was prepared in distilled water. Maximum
absorption value of urea was taken using double beam UV–vis
spectrophotometer. The standard curve of urea was taken at
maximum absorption. Urea solution of 2000 ppm was prepared in
distilled water and 2.0 g of candidate polymer was immersed in it
and kept overnight. Next day sample was taken out from the urea
solution and washed slightly with water to remove any surface
adhered urea molecules. The sample was dried in oven and its
evaluation of fertilizer release kinetics with respect to time was
studied using double beam UV–vis spectrophotometer. Concentration
of fertilizer release was carried-out after every 4 h, until the
equilibrium was achieved.
2.5. Mathematical analysis of urea release kinetics
Interpenetrating polymer network has properties to absorb and
retain a large amount of aqueous liquid in it. These properties make
them useful in controlled release of fertilizers. Simple and
sophisticated model have been developed to check the release
behavior of fertilizer from the interpenetrating polymer device as a
function of time. The most applicable mechanism of the solute
release behavior from the interpenetrating network is the diffusion
mechanism. Urea release behavior was determined through
empirical equation. Power law function given by Peppas et al. is
used to evaluate the fertilizer release behavior through the
interpenetrating polymer network.